src/black/debug.py

   1 from dataclasses import dataclass, field
   2 from typing import Any, Iterator, List, TypeVar, Union
   3
   4 from black.nodes import Visitor
   5 from black.output import out
   6 from black.parsing import lib2to3_parse
   7 from blib2to3.pgen2 import token
   8 from blib2to3.pytree import Leaf, Node, type_repr
   9
  10 LN = Union[Leaf, Node]
  11 T = TypeVar("T")
  12
  13
  14 @dataclass
  15 class DebugVisitor(Visitor[T]):
  16     tree_depth: int = 0
  17     list_output: List[str] = field(default_factory=list)
  18     print_output: bool = True
  19
  20     def out(self, message: str, *args: Any, **kwargs: Any) -> None:
  21         self.list_output.append(message)
  22         if self.print_output:
  23             out(message, *args, **kwargs)
  24
  25     def visit_default(self, node: LN) -> Iterator[T]:
  26         indent = " " * (2 * self.tree_depth)
  27         if isinstance(node, Node):
  28             _type = type_repr(node.type)
  29             self.out(f"{indent}{_type}", fg="yellow")
  30             self.tree_depth += 1
  31             for child in node.children:
  32                 yield from self.visit(child)
  33
  34             self.tree_depth -= 1
  35             self.out(f"{indent}/{_type}", fg="yellow", bold=False)
  36         else:
  37             _type = token.tok_name.get(node.type, str(node.type))
  38             self.out(f"{indent}{_type}", fg="blue", nl=False)
  39             if node.prefix:
  40                 # We don't have to handle prefixes for `Node` objects since
  41                 # that delegates to the first child anyway.
  42                 self.out(f" {node.prefix!r}", fg="green", bold=False, nl=False)
  43             self.out(f" {node.value!r}", fg="blue", bold=False)
  44
  45     @classmethod
  46     def show(cls, code: Union[str, Leaf, Node]) -> None:
  47         """Pretty-print the lib2to3 AST of a given string of `code`.
  48
  49         Convenience method for debugging.
  50         """
  51         v: DebugVisitor[None] = DebugVisitor()
  52         if isinstance(code, str):
  53             code = lib2to3_parse(code)
  54         list(v.visit(code))